A DC-AC voltage converter is an electrical system that changes a DC voltage to an AC voltage. The converted AC voltage may have any desired voltage level, waveform and frequency with the use of appropriate transformers, switching, filtering and control circuits. DC-AC voltage converters are used in a wide range of applications, from small switching power supplies in electronic devices such as computers to large electric utility high-voltage direct current applications that transport bulk power. DC-AC voltage converters are also commonly used to supply AC power from DC sources such as solar panels or batteries.
FIG. 1 shows a typical prior art DC-AC voltage converter 10, which operates at a relatively low frequency. Voltage converter 10 is relatively simple, but it suffers from significant disadvantages. A first disadvantage is cost, because it uses a low-frequency transformer 12 that requires a relatively large amount of copper for transformer windings. In recent years the cost of copper has increased, while the cost of power semiconductors has decreased. This trend is expected to continue. In addition, a low-frequency transformer has relatively low efficiency when it is configured with a relatively high winding turns ratio and is used for voltage step-up. An example of such configurations is a DC-AC voltage converter with a step-up transformer having a turns ratio of about 19:1 or more and a relatively low input voltage power source, for example about 10 to 20 volts DC.